1. Field of the Invention
The present invention relates to a three axis drive apparatus used for an automatic analyzer, an electronic parts mounting device, various processing machines and a conveying device.
2. Description of Related Art
As an example, in an automatic analyzer for analyzing a specimen of blood or urine which has been collected into a reaction container such as a well plate, it is necessary to conduct positioning by moving a distribution nozzle, which distributes liquid such as chemical into a reaction container, in three directions of X-axis, Y-axis and Z-axis.
Conventionally a positioning device which determines position of the distribution nozzle in the three directions of X-axis, Y-axis and Z-axis has an X-direction positioning mechanism for positioning in X-axis direction, a Y-direction positioning mechanism for positioning in Y-axis direction and a Z-direction positioning mechanism for positioning in Z-axis direction. The distribution nozzle is positioned at a predetermined position by operating these positioning mechanisms.
However, in the conventional device, a positioning mechanism for moving the distribution nozzle in the three axial directions is formed out of a combination of a linear guide with a ball screw. Therefore, at least two drive motors in the three drive motors for driving the ball screws are moved integrally with the distribution nozzle. Therefore, when the distribution nozzle is moved in the three axial directions, a Cable Bear (registered trademark in Japan) for protecting an electric power cable connected to the drive motor is dragged. Therefore, noise and dust are generated. Since at least two drive motors in the three drive motors are mounted on a movable portion of the mechanism portion, a weight of the movable portion is increased and it is difficult to move a member to be driven such as a distribution nozzle in the three axial directions at high speed.